It seems likely the UAV is less than 20 KG. It does not appear to be brightly coloured, or have a strobe.
If used to look for missing hillwalkers/climbers in Glenetive or Glencoe, it is likely to be operating at the same, or higher, height as that at which light aircraft fly through. Being so small, it will be difficult to see. It will be travelling at up to 100 mph. Unlike all other flying objects, there will be no lookout for me on the part of the UAV. The operator will be watching a screen showing the terrain. He will not have the desperate desire to avoid a collision at all costs, which on-board pilots have. He will not have an accurate picture of the position of an aircraft relative to his UAV, even if someone spots it, and draws it to his attention.
I am also wondering how stable its height and heading will be in the turbulence I often encounter in these glens.
An accident could perhaps lead to interesting liability cases against Strathclyde Police and the CAA.